EPO, a 30.4-kDa glycoprotein, regulates production of erythrocytes. It stimulates the proliferation and differentiation of erythroid precursor cells through binding to EPO receptors expressed on the surface of these cells. See Krantz, Blood 77(3):419-434 (1991) and Jelkmann, Physiol Rev. 72(2):449-489 (1992). EPO is a well-known therapeutic agent for treating anemia resulting from chronic renal failure or cancer chemotherapy.
G-CSF, a 19.6-kD glycoprotein, stimulates bone marrow to produce granulocytes. In addition, it promotes survival, proliferation, differentiation, and function of neutrophil granulocyte progenitor cells and mature neutrophils. G-CSF has been used for treating neutropenia for over twenty years. See Burgess et al., Int. J. Cancer 26(5):647-654 (1980), and Frampton, et al., Drugs 48(5):731-760 (1994).